The present invention relates chiefly to a hydraulic brake booster comprising a motor, preferably an electric motor.
It is known practice to produce hydraulic brake boosters (also known in English as hydroboost) which are supplied with pressurized hydraulic fluid from a hydraulic pump of a power steering device or of a master cylinder driven by a hydraulic brake booster as described for example in FR 2 727370.
Hydraulic boosters supplied by the power steering pump have very poor energy efficiency inasmuch as they are inserted in the hydraulic circuit of said pump with continuous circulation and an increase in pressure that is obtained by interrupting this circulation when a brake pedal is depressed. In addition, braking that coincides with the turning of the steering wheel reduces the effectiveness of the power steering, which the user finds unsatisfactory. The booster described in FR 2 727370 requires the use of a source of vacuum that is not necessarily available on modern-day vehicles, particularly diesel vehicles. In addition, a pneumatic booster occupies a great deal of space. Further, hydraulic boosters are limited by the saturation, the power and the travel of the pneumatic booster.
Other hydraulic boosters are described in DE 32 09 337, DE 43 38 906, DE 39 06 411 or EP 0 072 745.